Networking operating systems (NOSs) are designed to provide network processes to clients. Network services include the World Wide Web (WWW), file sharing, mail exchange, directory services, remote management, and print services. Remote management is a powerful service that allows administrators to configure networked systems that are miles apart. It is important to understand that these network processes are referred to as services in Windows 2000 and daemons in UNIX and Linux. Network processes all provide the same functions, but the way processes are loaded and interact with the NOS are different in each operating system.

Depending on the NOS, some of these key network processes may be enabled during a default installation. Most popular network processes rely on the TCP/IP suite of protocols. Because TCP/IP is an open, well-known set of protocols, TCP/IP-based services are vulnerable to unauthorized scans and malicious attacks. Denial of service (DoS) attacks, computer viruses, and fast-spreading Internet worms have forced NOS designers to reconsider which network services are started automatically.

Recent versions of popular NOSs, such as Windows 2000 and Red Hat Linux 7, restrict the number of network services that are on by default. When deploying a NOS, key network services will need to be enabled manually.

When a user decides to print in a networked printing environment, the job is sent to the appropriate queue for the selected printer. Print queues stack the incoming print jobs and services them using a first-in, first-out (FIFO) order. When a job is added to the queue, it is placed at the end of the waiting list and printed last. The printing wait time can sometimes be long, depending on the size of the print jobs at the head of the queue. A network print service will provide system administrators with the necessary tools to manage the large number of print jobs being routed throughout the network. This includes the ability to prioritize, pause, and even delete print jobs that are waiting to be printed.

File sharing
The ability to share files over a network is an important network service. There are many file sharing protocols and applications in use today. Within a corporate or home network, files are typically shared using Windows File Sharing or the Network File Sharing (NFS) protocol. In such environments, an end user may not even know if a given file is on a local hard disk or on a remote server. Windows File Sharing and NFS allow users to easily move, create, and delete files in remote directories.

File Transfer Protocol (FTP)
Many organizations make files available to remote employees, to customers, and to the general public using FTP. FTP services are made available to the public in conjunction with web services. For example, a user may browse a website, read about a software update on a web page, and then download the update using FTP. Smaller companies may use a single server to provide FTP and HTTP services, while larger companies may choose to use dedicated FTP servers.

Although FTP clients must logon, many FTP servers are configured to allow anonymous access. When users access a server anonymously, they do not need to have a user account on the system. The FTP protocol also allows users to upload, rename, and delete files, so administrators must be careful to configure an FTP server to control levels of access.

FTP is a session-oriented protocol. Clients must open an application layer session with the server, authenticate, and then perform an action, such as download or upload. If the client session is inactive for a certain length of time, the server disconnects the client. This inactive length of time is called an idle timeout. The length of an FTP idle timeout varies depending on the software.

Web services
The World Wide Web is now the most visible network service. In less than a decade, the World Wide Web has become a global network of information, commerce, education, and entertainment. Millions of companies, organizations, and individuals maintain websites on the Internet. Websites are collections of web pages stored on a server or group of servers.

The World Wide Web is based on a client/server model. Clients attempt to establish TCP sessions with web servers. Once a session is established, a client can request data from the server. HTTP typically governs client requests and server transfers. Web client software includes GUI web browsers, such as Netscape Navigator and Internet Explorer.

Web pages are hosted on computers running web service software. The two most common web server software packages are Microsoft Internet Information Services (IIS) and Apache Web Server. Microsoft IIS runs on a Windows platform and Apache Web Server runs on UNIX and Linux platforms. A Web service software package is available for virtually all operating systems currently in production.

Domain Name System (DNS)
The Domain Name System (DNS) protocol translates an Internet name, such as www.cisco.com, into an IP address. Many applications rely on the directory services provided by DNS to do this work. Web browsers, e-mail programs, and file transfer programs all use the names of remote systems. The DNS protocol allows these clients to make requests to DNS servers in the network for the translation of names to IP addresses. Applications can then use the addresses to send their messages. Without this directory lookup service, the Internet would be almost impossible to use.

Dynamic Host Configuration Protocol (DHCP)
The purpose of Dynamic Host Configuration Protocol (DHCP) is to enable individual computers on an IP network to learn their TCP/IP configurations from the DHCP server or servers. DHCP servers have no information about the individual computers until information is requested. The overall purpose of this is to reduce the work necessary to administer a large IP network. The most significant piece of information distributed in this manner is the IP address that identifies the host on the network. DHCP also allows for recovery and the ability to automatically renew network IP addresses through a leasing mechanism. This mechanism allocates an IP address for a specific time period, releases it, and then assigns a new IP address. DHCP allows all this to be done by a DHCP server which saves the system administrator considerable amount of time.